High speed film printer



June 10, 1941. F. w. ROBERTS HIGH SPEED FILM PRINTER 2 Sheeis-Sheet 1 Filed May 1, 1939 can 0 NB mo P K m w. w P r ATTORNEY.

June 1941- F. w. ROBERTS HIGH SPEED FILM PRINTER Filed May 1, 1939 2 Sheets-Sheet 2 Patented June It), 1941 HIGH SPEED FILM PRINTER Frederick William Roberts, New York, N. Y., al-

algnor to Warner Pietnrea York, N. Y., a corporation of Delaware New Application May 1, 1035; Serial No. 211,040

(Cl. as

23 Claims.

This invention relates to printing apparatus for printing from one film to another and particularly refers to apparatus for printing motion picture films wherein the intensity of illumination of the printing light beam is varied throughout the printing operation.

In successively cinematographing different scenes,it is found that the average density of the resulting negative film or films obtained often varies from one scene to another due to variations in lighting, adjustment of the camera lens opening, camera speed, and the like. It is therefore necessary to control the density of the corresponding scenes throughout the resulting positive film, especially for adjacent scenes thereon so as to prevent any great change in density when passing from one scene to the next. Again, it may be desirable to change the density of a certain scene on the film to portray a particular dramatic efi'ect.

A method commonly employed in controlling the average density of a positive print is to vary the intensity of illumination of the printing light beam during the printing operation. This is commonly accomplished by employing an automatically or semi-automatically operated rheostat in the printing lamp circuit wherein pre-set resistances are successively placed in the lamp circuit under control of notches provided along the negative film. These notches are previously placed along the negative at points where it is desired to change the printer light intensity. The resistances are either pre-arranged so that apparatus operated by the film notches merely switches these resistances in the lamp circuit or they are actually adjusted a certain amount by the apparatus operated by the film notches.

In any event, since an incandescent filament lamp is generally employed for printing, a certain length of time is required for the intensity of illumination of the printing lamp to change from one value to another, due to the thermal inertia of the lamp filament. Thus, where the motion picture films are run past the printing light beam at a relatively high speed, this lag in illumination response of the printing lamp prevents the desired printing illumination from being obtained at the start of each new scene or section on the film wherein the illumination is to be changed. For example, if the films being printed are run at 150 feet per minute, four or five film frames at the start of a new scene or section wherein the illumination is to be changed may pass the printing point before the printing illumination reaches the value determined for that particular new scene. Thus, these four or five film frames will be either over-exposed or under-expend, depending on whether the printing illumination is decreased or increased for the new scene. Consequently, this lag or thermal inertia of an incandescent printing lamp limits the speed at which the printing machine can be run.

Furthermore, when running films during the printing operation at a relatively high speed, i. e. to 200 feet per minute, a larger lamp having a heavier filament must be used than when the films are run at a slower speed due to the fact that the intensity of printing illumination must be increased as the film speeds are increased. Thus, the thermal inertia or lag is greater for high speed film printers due to the increased size of the lamp filament.

When controlling the illumination of the printing light beam, it is necessary to keep a constant check on the printing operation to make sure that the various elements of the printer are actuated correctly to obtain a correct exposure for each scene. This is especially true when the illumination is automatically controlled since, in that event, if one scene is printed with a wrong exposure, the remainder of the film scenes will also usually be printed with the wrong exposure, thereby ruining the remainder of the printed film. When the printing apparatus is run at a relatively slow speed, the operator can visually check the exposure of each of the various scenes against a table indicating the correct exposure for each scene. However, at relatively high printing speeds, this is practically impossible since a film scene may then pass through the printing apparatus in less than a second, which would be too fast to enable the operator to check the operation of the printing apparatus for that particular scene.

One object of the present invention is to quickly vary the intensity of illumination of a film exposing system.

Another object is to obtain a correct intensity of illumination of a printing'light beam before printing with said beam.

Another object is to successively direct the light beams from a pair of printing lamps onto a pair of films to be printed.

Another object is to automatically employ alternate ones of a pair of printing lamps to print from one film to another when predetermined poirltitons of one of the films passes a certain po Another object is to automatically stop a printing machine when a part thereof does not function properly.

The manner in which the above and other objects of the invention are accomplished will be readily understood on reference to the following specification read in conjunction with the accompanying drawings wherein:

Fig. 1 is a diagrammatic view, partly in perspective, illustrating the printing apparatus and circuit connections therefor embodying the present invention.

Fig. 2 is a transverse sectional view through a printing machine embodying the present invention.

Fig. 3 is a sectional view through the printing machine and is taken substantially along the line 33 of Fig. 2.

Fig. 4 is a sectional plan view taken substantially along the line 4--4 of Fig. 2.

The invention is illustrated in the drawings as applied to a continuous contact film printing machine for printing pictures on a motion picture film. A developed negative film A having picture frames therealong and a light sensitive film B are passed in contact past a printing point P (Fig. l) by suitable film driving means including a printing sprocket |3. Sprocket |3 comprises two spaced sprocket wheels II and I2 mounted on a sprocket shaft i3 which is driven through a worm and worm wheel pair H by a three phase synchronous motor l5. However, any suitable motor may be employed with corresponding power circuit changes therefor. The sprocket shaft I3 is journalled in a bearing i3 (Fig. 4) formed in a printer casing l1.

Casing |1 forms a horizontally extending cylindrical printing chamber |3 housing the sprocket l3 and an adjacent vertically extending cylindrical printer lamp chamber 23. An opening I3 in a wall I3 communicates the chambers l3 and 23 to allow the printing light beams to pass from one chamber to the other. A pair of printing lamps 2| and 22 are provided in the chamber 23 and are carried by lamp mounts 23 and 24, respectively mounted on a vertical wall 25 depending from a circular flange 23 covering the chamber 23. Flange 23 is removably secured to the top of the casing I1. by screws 23' whereby the lamp assembly may be removed from the casing 23 to replace or adjust the lamps 2| and 22. Wall 25 forms a light baffle to prevent undesired light from the lamps 2| and 22 from passing into the printing chamber l3. Each of the lamps 2| and 22 is shown as having a cylindrical base 21 (Fig. 2) adjustable rotatably and vertically in its respective mount and adapted to be clamped in any adjusted position by a clamp screw 23. Each of the lamp mounts 23 and 24 is individually supported from the wall 25 by a screw 23 (Fig. 3) passing through an elongated slot 33' in the wall 25 whereby the mount and its respective lamp may be adjusted laterally.

A reflecting prism 33 is supported from the wall 25 by a bracket 3| to simultaneously reflect the light from the lamps 2| and 22 through spaced openings 32 and 33, respectively, in the wall 25. The light beams reflected by the prism 33 from the two lamps are directed in a converging manner toward a superposed position on the films A and B at the printing point P.

A light shutter 34 having an opening 35 therein is mounted on a stub shaft 35 journalled in a bearing provided in the wall 25. A pair of electro-magnets 31 and 33 are supported on the wall 25 on opposite sides of the shaft 35 by brackets 31' and 33', respectively, and are adapted to alternately attract an armature .33 secured to the shaft 33 and extending on opposite sides thereof to move the shutter 34 to alternately align the shutter openings 35 with the openings 32 and 33 in the wall 25. Movement of the shutter 34 is limited by means of a pin 43 extending upwardly from the hub of the shutter 34 and adapted to engage either of a pair of spaced pins 4| and 42 extending from the wall 25. The shutter assembly including shutter 34 is made as light as possible so as to minimize inertia and enable quick response thereof to the magnets 31 and 33.

It will be seen from the above that energization of the magnet 31 will cause the shutter 34 to be moved into aposition wherein the opening 35 therein is aligned with the opening 32 in wall 25 so as to allow the light beam 2|a from the lamp 2| to be directed onto the films at the printing point P while shuttering the light beam 22a from the lamp 22. Alternately, when the magnet 33 is energized the shutter 34 will be moved into a position to shutter the light beam 2|a and allow the light beam 22a to be directed onto the films at the printing point.

The lamps 2| and 22 and magnets 31 and 33 are cooled by a centrifugal blower generally indicated at 44. The casing 45 of blower 44 is secured to the top of the circular flange 23 by screws 43 and has an opening 43 therein aligned with a similar opening in the flange 23 whereby a draft of air may be passed therethrough. A fan 41 mounted in the casing 45 and driven by a motor 43 mounted on top of casing 45 is adapted to exhaust air down through the opening 43 through an outlet 43 formed in the blower casing 45.

Referring to Fig. 1 the filament of the lamp 2| is provided in series with a master rheostat 53, the energizing coil of a lamp failure relay 5|, an individual rheostat 52, and an automatic rheostat, diagrammatically indicated at 53, across a direct current power circuit 54. The filament of lamp 22 is similarly connected in series with the master rheostat 53, the energizing coil of a second lamp failure relay 55, an individual rheostat 51, and a second automatic rheostat 53, across the power circuit 54.

The resistances 52 and 51 are provided to permit accurate balancing of the illumination of the two lamps 2| and 22. The master rheostat 53 permits common adjustment of the brilliance of the two lamps to compensate for blackening and aging of the lamps.

The automatic rheostat 53 is of a type well known in the art comprising a resistance 53 having parts thereof tapped to closely adjacent vertical metallic conductor strips 53. Equispaced holes 33 are provided in each of the strips 53 and are adapted to have contact plugs 3| fitted therein. A metallic contact bar 32 is shown as being movable vertically along the strips 53, but out of contact therewith by means of an endless chain 33 passing over spaced sprockets 34 and 35. The bar 32 is adapted to be moved a distance equal to the spacing of the holes 33, one step at a. time, by means of a pawl and ratchet device 33 operatively connected to the sprocket 35 and energized by a stepping magnet 51. As the contact bar 32 is moved step by step down the length of the various strips 53, it contacts the various previously positioned plugs 3| provided in different ones of the strips 53 and thus completes the lamp circuit through a flexible conductor 33. Thus, as the contact bar 32 is stepped downward, the

s,su,ses

brilliance of the lamp 2i is varied according to the positions of the various plugs ll.

The automatic rheostat It is identical with that of II and comprises a resistance II tapped to various conductor strips ll adapted to receive contact plugs 12. Plugs 12 are successively contacted by a contact bar 13 which is stepped by means of a pawl and ratchet device ll operated by a stepping magnet 1|. Contact bar 12 completes the lamp circuit through a flexible conductor It. v

The stepping magnets 01 and II are placed in circuit with a slow release relay It and a bank of contacts E of a selector switch generally indicated at 11. Switch I1 is preferably of a type known in the art as a Strowger rotary switch, and comprises three semi-circular banks of contacts E, l" and G contacted by arms 8|, .2 and II, respectively. These arms are stepped from one contact to the next in unison by a pawl and ratchet device 84 actuated by a stepping magnet 26. Stepping magnet 85 is provided in series with a breaker switch I! and a power relay l'l' across the direct current supply circuit I.

Breaker switch It rides against one edge of the negative film A only and is successively actuated by successive ones of a series of notches (as shown at 81) previously formed along the edge of the negative film to momentarily close the contacts thereof and consequently, (assuming the power relay .1 to be closed) to transmit an impulse to the stepping magnet II to step arms ll, 82 and 82 from one contact to the next. A condenser Ill and resistance 80' are provided in series with each other across the contacts of switch I. to reduce arcing. The switch I is adapted to be adjusted in position toward or away from the printing point P along the dim path in a manner not shown for diii'erent film peeds.

The various alternate contacts El, E2, E8, etc. of the bank E are connected to one side of the stepping magnet 81 whereas the alternate contacts E2. E4, El, etc. are connected together and to one side of the stepping magnet 18. The other side of each of the magnets 81 and II is connected at i2! to one of the contacts of the relay ll which, when closed will transmit an impulse to either of the magnets 81 or II, depending upon the position of the arm 8| of the contact bank E (assuming the power relay is to be closed as described hereinafter). The energizing coil of relay is placed in series with a second breaker switch 88 identical with that of II and also adapted to be momentarily closed by the various notches 81 along the negative film. A condenser I20 and resistance l2l' are placed in series with each other across the contacts of switch 28 to reduce arcing. Switch 88 is connected in series with the energizing coil of relay I8 and a set of contacts of the power relay 8! across the supply circuit 4 so as to momentarily energize the relay II when a notch .1 in the negative film A actuates switch It. Switch It is adapted to be adjusted in position along the film path toward and away from the printing point P in a manner not shown, but it is preferably maintained at such a distance from the breaker switch I. that a lapse of about one sixteenth of a second will occur between the tripping of these two switches It and as by a single notch s1 in the fllm a. Relay it is adjusted so as to remain closed approximately one sixteenth of a second after the switch 82 has momentarily closed and again opened, thus insuring that a sumcient amount of current is supplied to either magnet II or 'II to actuate the respective contact bar '2 or II operated thereby. Indicator lamps I20 and I" are placed in shimt acrossthesteppingmagnetsll and 'lltoindicate the operation thereof.

The alternate contacts GI. GI, GI etc. of the bank of contacts 0 of switch I! are connected together and in series with the energizing coil of a quick acting shutter relay ll to one side or the supplyeircultll. Thearmllofbankflisconnected by a line I! to the other side of the nipply circuit ll. Thus, when the am .8 is stepped into contact with any of the above contacts GI, 02, etc. the relay .0 will be closed. The contacts of relay OI are provided in series with the shutter actuating magnet across the supply circuit '4 so as to cause the opening ll in shutter II to be aligned with the opening 82 in wall 2| when this relay I. is closed.

The alternate contacts 02, G4, G0, etc. are connected together and in series with the energizing coil of a second quick acting shutter relay OI to one side of the supply circuit 54. Thus, when the arm it engages any of these contacts (32, G4, etc. the circuit through the coil of relay II will be closed to close this relay. The contacts of relay 2| are provided in series with the shutter magnet 21 across the supply circuit '4 so as to cause this magnet 21 to be energized when the arm ll engages any of the contacts G2, G4, etc. Indicator lamps I22 and I24 are placed in shunt across the shutter magnets 21 and II, respectively to indicate which printing lamp 2| or 22 is printing at any particular moment.

The arm '2 of the bank of contacts F of switch 11 is electrically connected by a line I22 in series with the energizing coil of a second slow release relay 22 to one side of the supply circuit 84. Relay I2 is preferably so adjusted that its contacts will remain closed for about one-eighth of a second after the coil thereof has been energized. The various contacts Fl, F2, F3, F4, etc. of the bank F are connected to successive contact plugs Ila, lib, "b, "c, etc. immovably secured on strips 24 and ii of insulating material in a manner described hereinafter, to form part of a mislight checking circuit. Strip N is provided in the automatic rheostat ll parallel to and closely adjacent one of the conductor strips 52. The plugs "a, "b, etc. are equi-spaced along the strip 24 and in line with the rows of holes I in the conductor strips ll whereby, when the contact bar 02 is moved downward step by step along the various strips, successive ones of the plugs 28a, 22b, etc. will be contacted by the contact bar. Likewise strip is placed closely adjacent one of the conductor strips II in the automatic rheostat II and is adapted to have the successive ones of the plugs "a, b, etc. thereon (spaced identically the same as the holes along the strips 1|) contacted by the contact bar It as it is moved downward step by step. The contacts Fl, F2, F2, etc. are connected as follows to the various plugs on strips 24 and 25. Contact Fl is connected to plug a; contact F2 is connected to plug llb; contact F2 is connected to plug lib; contact F4 is connected to plug "c, etc. Due to the fact that each of the automatic rheostats may have a hundred or more scene change settings, 1. e. one hundred or more holes Oil provided along each conductor strip thereof, it is impracticable to assign a separate contact Fl, F2, etc. to each separate contact plug on the insulated strips 94 and II. To overcome this, I make use of a rotary switch 1" having sixteen contacts F2, F2, etc. and

so arrange the connections from the rotary switch F to each of the automatic rheostats 53 and 58 that eight of the alternating contacts on switch F serve one of these automatic rheostats and the remaining eight alternate contacts on switch F serve the other automatic rheostat. Therefore, each of the sets of eight contacts on rotary switch F may serve a very large number of contacts on each of the automatic rheostats 53 and 58. For this purpose, I connect the contacts on each of the automatic rheostats 53 and 58, respectively, in groups in parallel to the rotary switch F in such manner that after the contact bar of either of the automatic rheostats 53 and 58 has made eight steps, that bar will complete a connection to the same contact on the rotary switch F as was completed when that bar was in its initial position for that particular series of eight steps. Therefore, contact plugs 83a, 831', etc. are connected together and contact plugs 88b, 8331, etc. are connected together, etc. Also, contact plugs 88a, 881', etc. are connected together and contact plugs 88b, 88?, are connected together etc. Thus, when the arm 82 is contacted in series with either the contact arm 82 or the contact arm 18, a circuit will be closed through the coil of the relay 82 to close the same for the purpose described hereinafter.

It will be seen from the above that two counting devices, in effect, are provided. One of these comprises the plugs 83 and 88 provided on the strips 88 and 85, respectively, which are successively contacted by the arms 82 and 13, respectively, actuated under control of the breaker switch 88. The other of these counting devices comprises the rotary switch 11 having the series of contacts FI, F2, etc., which switch is actuated by the other breaker switch 88. Therefore, there are two separate electric channels which must be actuated in timed relation with each other to maintain the apparatus in operation.

The motor I5 is driven by a three phase alternating current supply circuit 81. Two lines 88 and 88 of the supply circuit 81 pass through the relay 81 and have provided in series therewith a pair of starting resistances, or reactances I88 and |8|, respectively, whereby the motor I5 may be brought slowly up to its normal operating speed. The reactances or resistances I88 and |8| are adapted to be short circuited by a time delay relay I82, the energizing coil of which is adapted to be connected in circuit across lines 88 and 88 of circuit 81 by power relay 81'. Relay |82 is so adjusted that its contacts close at approximately three seconds after the coil thereof is energized by the power relay 81'.

The energizing coil of power relay 81' is provided in series with a start switch I83, the contacts of the lamp failure relays 5| and 55 and the slow release relay 82 across the direct current supply circuit 58 so as to close the relay 81' when the start switch I83 is closed (assuming that a master switch I88 in the circuit 58 and the relays 5|, 55 and 82 are closed.)

A brake drum I85 mounted on the drive shaft I88 of motor I5 is adapted to be engaged by a brake shoe |81 normally held in frictional braking engagement therewith by a spring I88. Shoe I81 is adapted to be retracted from braking engagement by a solenoid I88 placed in series with'the relay 81' across the power circuit 58.

A small printing lamp 8 focused by means of a lens I in the path of the edge or code numbers along the edge of the negative film A is provided in shunt with the solenoid I88 .50 as to be illuminated when the power relay 81' is closed. Lamp 8 thus serves to print the edge numbers occurring between one set of sprocket holes and the adjacent edge of negative A onto the film B.

The arms 8|, 82 and 88 of rotary switch 11 are adapted to be rotated into the starting position shown by the full lines of Fig. 1 wherein the arms 8|, 82 and 83 engage the contacts El, FI, and GI, respectively, by a homing circuit comprising normally open push button 2 placed in series with a homing device generally indicated at 3 across the power circuit 54. Homing device III may be of any well known type but is illustrated as comprising a normally closed switch III adapted to be open by a cam |I5 when the arms 8|, 82 and 88 have reached their starting positions. Arm 5 is operatively connected to the arm 8| in a manner not shown and is rotatable therewith. Switch III is provided in series with a second normally closed switch I21 adapted to be opened by the stepping magnet 85 when energized. When the push button H2 is closed to energize the homing circuit (assuming the arms 8|, 82 and 83 to be out of engagement with the respective contacts El, FI and GI) the stepping magnet 85 will be energized to cause the pawl and ratchet device 88 to step the arms from one contact to the next. This action will cause the stepping magnet 85 to open switch I21. This will de-energize magnet 85, causing the switch I21 to again close and preparing the pawl and ratchet device for the next step. When the arms reach their starting positions the cam 5 will open switch I to thus stop the operation of the homing device.

Operation The printing apparatus is set up as follows. The negative film to be printed is first checked to determine the desired printer light intensity for each scene or section thereon. The negative is then notched as at 81 along one edge thereof at the points where changes in printer light intensity are to occur. These notches are not placed at the exact point where such printer light intensity is to change but are placed behind such point a distance equal to the distance between the breaker switch 88 and the printing point P plus a distance determined by the time delay caused by the rotary switch 11, the quick acting relays 88 and 8| and the shutter 88.

Note is made of the desired printing light changes for the various scenes and the various plugs 8| in the automatic rheostats 53 and 58 are placed in the corresponding positions along the conductor strips 58 and 1|, respectively. These various plugs 8| are placed as follows. The printer light intensity to be placed in the printer lamp circuit of the first scene is determined and a contact plug as at is placed accordingly in the top hole of the one of the strips 1| of automatic rheostat 58 which corresponds to the particular resistance required. Thus the lamp 22 will be illuminated at this desired intensity for th first scene. A plug as at 8|a is then placed in the top hole of the one of the conductor strips 58 of automatic rheostat 53 which corresponds to the particular resistance required for the second scene. Thus, when the contact bars 82 and 18 are moved to their uppermost positions the lamp 22 will be illuminated at the correct intensity for the first scene and the lamp 2| will be illuminated at the correct intensity for the second scene. A plug as at 12b is then placed in the second hole of the one of the strips H of rheostat I. which corresponds to the particular resistance required for the third scene. This procedure is followed for all oi the scenes or sections 01' the film A wherein the printing light intensity is to be changed. Thus, it will be seen that the printer light intensity for the successive odd numbered scenes are determined or set up by the successive plugs I! along the strips ll of rheostat 56 while the light intensity oi the successive even numbered scenes are determined or set up by the successive plugs 6| on the automatic rheostat ll. One more plug is placed in the rheostat opposite the one in which the plug corresponding to the last scene is placed so as to prevent one lamp circuit irom being opened when the last scene is being printed.

The first step in the operation of the printing apparatus is to thread the negative film A and the sensitive film B in contact with each other in the printing apparatus and to raise the contact arms I and II oi automatic rheostats I8 and 60, respectively, to their upper positions illustrated by the full lines in Fig. l. The master switch I in the direct current supply circuit 54 is then closed to close both printing lamp circuits, thereby causing the lamp 22 to be illuminated at the desired intensity for the first scene and the lamp II to be simultaneously illuminated at the intensity predetermined tor the second scene. Closing of the lamp circuits also causes the lamp failure relays II and I to be closed, assuming, of course, that the lamps 2i and 22 are not burnt out.

The push button I is then closed and held in this position for a short time to cause the homing device lit to rotate the arms ll, 82 and 08 into their starting position as indicated by the full lines of Fig. 1. when in this position a circuit is completed through the energizing coil or the slow release relay 82, line I22, the arm 02 of the bank 0! contacts F and the contact Fl to the first contact plug "a on the insulator strip 94 oi automatic relay '3, and through the contact bar 62, the circuit being provided across the direct current supply circuit 54, thus causing the relay I! to close.

Also, when the arms ll, 82 and 83 are in their starting position, the arm I: will engage the contact GI oi the bank G to complete a circuit through the quick acting relay 9| across the power supply circuit 54, thus closing this relay to cause the magnet 38 to attract the armature II and thus move the mask 34 into a position wherein the opening 35 therein is aligned with the opening It allowing the beam of light from the lamp 2! (illuminated at the desired intensity for scene #1) to be passed therethrough and impinge upon the films A and B at the printing point P.

Thereafter, the starting switch III! is closed to close the circuit through the energizing coil of the power relay .1 (assuming the relays I, I! and 92 are closed) thereby closing relay l1. As the relay 81' is closed three phase current is supplied to the motor II to start the same while simultaneously releasing the brake I01 and illuminating the edge numbered printing lamp Ill. Approximately three seconds after the starting switch II! has been closed the time delay relay I 02 will close, thereby short circuiting the starting resistances ill and ill to bring the motor ll up to its normal printing speed.

Thus, the first scene or section 01' the film A will be printed onto the film B by light from the printing lamp 22 while the light from the lamp 2|, (illuminated at the intensity predetermined for the next scene) is shuttered by shutter to.

As the first notch 81 passes and actuates the first breaker switch ll, an impulse is momentarily transmitted to the stepping magnet 85 of the rotary switch l'l so as to rotate the arms II, I! and it into their next successive positions in engagement with the contacts E2, F2, and (32, respectively. In this position, a circuit will be closed through the arm 83, contact G2, and the quick acting relay ll so as to energize the shutter magnet 31 to quickly throw the shutter 34 into its alternate position wherein the light beam from the lamp 2| will be directed to the films. ltwillbenotedthatsincethearmllhasbeen moved to the con-tact 1"! the circuit through the energizing coil 01! the slow release relay I: will be broken since the contact arms I! and II are still in their upper positions (as illustrated in Fla. 1). However, due to the slow release characteristic of relay 82, it will maintain the contacts thereof closed tor a period of approximately one-eighth of a second after the circuit through the energizing coil thereot has been broken. Approximately one-sixteenth of a second aiter the breaker switch I! has been momentarily closed by a notch 01 in the film A, this'notch will momentarily close the second breaker switch ll whereby to energize the slow release relay It. As relay It is closed, it will close a circuit through the stepping magnet ll of automatic rheostat 58, through the contact E2 and arm ll across the supply circuit 54 so as to cause the contact arm II to he stepped down to the next contact button no to cause the lamp 1! (now shuttered) to be illuminated at an intensity predetermined tor the third scene. Since the contact .2 has moved to the contact F2, a circuit will now be resumed through the arm II, contact Plug b and the contact arm I! to again energize the relay .2. Since this action takes place in less than one-eighth oi a second, the relay does not have a chance to open under normal operation. However, it any 01 the stepping devices ll, 66 or H, or the breaker switches II, or 88, or the relay ll fail to function properly, or if the D. C. power supply ll should fail, the circuit through the coil of relay 8! will be interrupted more than one-eighth second, thereby allowing the relay to open to cause the motor I! to automatically stop.

As the second notch ll passes the breaker switch 88, the rotary switch 11 is again moved one step to cause the shutter 34 to again uncover lamp 2! (now illuminated at the predetermined intensity for the third scene). Switch 11, at this time, also prepares the circuit for the stepping magnet i1 and for the slow release relay 92. When the second notch '1 passes the breaker switch I, the relay II is closed to cause the magnet 81 to step the contact bar 02 down to the next level, thereby completing the mislight checking circuit through the relay .2.

The above operation is continued for the successive scenes until the last scene is reached. When the last notch (punched in the edge of film A at the end of the last scene) aetuates the breaker switch I. the rotary switch will be stepped as usual, but when the second breaker switch It is actuated to step the corresponding one of the contact bars 62 or II downward to the next contact level, one oi the lamp circuits will be opened due to the absence or atcontact plug at this level.

Thus the motor i is automatically stopped.

The checking or counting device embodied in the present invention may be incorporated in any printer apparatus using an automatically opalso be employed in projection printers, step by step printers, or other film exposing devices. When the invention is employed in step by step printers, the operation of switching from one light to the other may be so timed as to occur during the shuttered period, that is, during the period when the printing and printed films are being stepped to position next successive film frames in the printing aperture during which period a separate shutter (not shown) would be employed to shutter the printing beam. Also, of course, the invention may be applied to printing apparatus for printing color picture films. In connection with printing color films, the invention is very important due to the fact that the density control of color films is very critical, necessitating frequent and accurate adjustments of the printing light illumination.

Furthermore, the invention may be applied to sound track printers where it is desired to change the density of certain parts of'the sound track being printed. Therefore, I desire it to be understood that modifications may be made and that no limitations upon the invention are intended other than are imposed by the scope of the appended claims.

I claim:

1. Film printing apparatus comprising the combination of means forming a film gate, a pair of printing lamps, means for alternately directing the light beams from said lamps onto said film gate, means for illuminating said lamps and film operated means for varying the intensity of illumination of one of said lamps when the light beam of the other of said lamps is directed onto said film gate.

2. A film printing apparatus comprising the combination of means iorming a film path, means forming a pair of printing light beams directed in super position on the same side of said film path, a shutter in the path of each of said beams, means for actuating said shutter to alternately shutter said beams, and means under control of said last mentioned means for varying the intensity of illumination of said beams.

3. A film printing apparatus for printing from a developed film to a sensitized film comprising means forming a film path, means for passing said developed film through said path, a pair of printing lamps, means for directing beams of light alternately from said lamps on said developed film, and means under control of said film for actuating said last mentioned means.

4. Film printing apparatus for printing from a printing film to a sensitized film, one of said films having notches therealong, which comprises the combination of means for moving said films in printing relation through a predetermined path, a pair of printing lamps, film controlled means for illuminating said lamps at different (intensities, and means under control of said notches for alternately directing the light beams from said lamps on said printing film, whereby to successively print said films with light having varying itnensities.

5. Film printing apparatus for printing from a printing film to a sensitized film, one of said films having notches therealong, which comprises the combination of means for moving said films in printing relation through a predetermined path, a pair of printing lamps, means for concomitantly illuminating said lamps, means under control of said notches for alternately directing the light beams from said lamps toward the same point in the path of movement of said films, and means under control of said notches for changing the intensity of illumination 01' one of said lamps when the beam from the other of said lamps is directed onto said film.

6. Film printing apparatus comprising the combination of means for moving a developed film and a sensitized film in printing relation through a predetermined path, a printing lamp, means for directing a light beam from said lamp toward said films to print said films, a shutter adapted; to intercept said light beam, means under control of a notch in one of said films for moving said shutter into light intercepting position, means under control of a second notch in one of said films for moving said shutter out of light intercepting position, and means under control of one of said notches for varying the intensity of illumination of said lamp when said light beam thereof is intercepted.

'7. Film printing apparatus comprising the combination of means for moving a developed film and a sensitized film in printing relation through a predetermined path, a pair of printing lamps, means for directing the light beams from said lamps onto said films at the same point in said path or said films, a shutter, means actuated by a notch in one of said films for actuating said shutter to intercept one of said beams, means actuated by .a second notch in one of said films i'or actuating said shutter to intercept the other of said beams, and means under control of one of said notches for varying the intensity of illumination of one of said lamps when the beam thereof is intercepted.

8. Film printing apparatus comprising the combination of means for moving a developed film and a sensitized film in printing relation,

. means for directing a pair of printing light beams onto said films, a shutter, means comprising a shutter circuit adapted to move said shutter to intercept one of said beams, means comprising a second shutter circuit adapted to move said shutter to intercept the other of said beams, switching means adapted to be actuated by a notch in one of said films for energizing said first mentioned shutter circuit and adapted to be actuated by a second notch in one of said films for energizing said second shutter circuit.

9. Film printing apparatus comprising the combination of means i'or moving a developed film and a sensitized film in printing relation, a'pair of printing lamps, a power circuit for illuminating said lamps, means for directing the light beams from said lamps alternately onto said films, a selector switch movable in different positions and a stepping magnet therefor, switch means and connections therefor adapted to be actuated by notches in one of said films for energizing said magnet, means comprising a circuit adapted to be energized by said selector switch when in one position thereof for actuating said second mentioned means to direct the light beam from one oi said lamps onto said films, means comprising a second shutter circuit adapted to be energized by said selector switch when in a difi'erent position thereof to direct the light beam from the other of said lamps onto said films. a variable resistance in said power circuit, and means comprising said selector switch when in one position thereof for varying the intensity of illumination of one of said lamps when the light beam from the other of said lamps is directed onto said films.

10. Film printing apparatus according to claim 9 comprising a relay and circuit connections therefor ior actuating said first mentioned means, and a circuit for energizing said relay comprising in series, said selector switch and said variable resistance.

11. Film printing apparatus comprising the combination of means for moving a printing film and a sensitized film in printing relation through a predetermined path, a pair of printing lamps, means for alternately directing the light beams from said lamps onto said films for printing said films, circuit means comprising a selector switch and a stepping magnet therefor for energizing said last mentioned means, an energizing circuit for said magnet comprising a switch adapted to be actuated by notches in one of said films, and means for varying said lamps under control of the stepping of said switch.

12. Film printing apparatus comprising the combination of means for moving a printing film and a sensitized film in printing relation through a predetermined path, means for directing a pair of printing light beams onto said films for printing said films, a shutter means adapted in one position to intercept one of said beams, and adapted in another position to intercept the other of said beams, means comprising a circuit for moving said shutter means into one of said positions, means comprising a second circuit for moving said shutter means into the other of said positions, a selector switch adapted in one position to energize one of said circuits and adapted in another position to energize the other of said circuits, a stepping magnet for said selector switch, and an energizing circuit for said magnet comprising a switch adapted to be actuated by notches in one of said films.

13. Film printing apparatus comprising the combination of means for passing a printing film and a sensitized film in printing relation through a predetermined path, a printing lamp, a second printing lamp. an electric power circuit for illuminating said lamps, means comprising a selector switch adapted in one position of said switch to direct the light beam from said first mentioned lamp onto said films at a printing point to print said films and adapted in a second position of said switch to direct the light beam from said second lamp onto said films at said printing point to print said films, means for successively moving said selector switch from one of said positions to the other when successive predetermined portions of one of said films pass said printing point, a variable resistance device in said circuit for controlling the illumination of said first lamp, a second variable resistance device in said circuit for controlling the illumination of said second lamp, means comprising said switch when in said first mentioned position of said switch for actuating said second varablc resistance device and means comprising said switch when in said second position of said switch for actuating said first mentioned variable resistance device.

14. Film printing apparatus according to claim 13 wherein said means for successively moving said selector switch comprises an energizing circult and a switch in said last mentioned circuit adapted to be actuated by notches in one oi said 15. Film printing apparatus comprising the combination of means for passing a printing film and a sensitized film in printing relation through a predetermined path, a circuit comprising switching contacts of a relay for energizing said means, a pair of printing lamps adapted to print said films at a certain point in said path, an electrical power supply for said lamps, respective means for individually varying said electrical power for said lamps whereby to individually vary the intensity of illumination thereof, means comprising a selector switch adapted in one position thereof to actuate one of said last mentioned means and adapted in another position thereof to actuate the other of said last mentioned means, means for alter- I nately moving said switch into said two mentioned positions when successive predetermined parts of said films pass said point. separate circuits for energizing said relay to close said contacts thereof, and means whereby said switch is adapted to energize one of said circuits when in one of said positions thereof and adapted to energize the other of said circuits when in the other of said positions thereof.

16. In a film printing apparatus, the combination of means forming a beam of light, means for passing a film through said beam, means for varying the intensity of illumination of said beam. film controlled means for preparing said intensity varying means for operation, and other film controlled means for completing actuation of said last mentioned means.

17. In a film printing apparatus, the combination of means forming a beam of light, means for passing a film having notches therealong through said beam, means for varying the intensity of illumination of said beam, a circuit controlling said last mentioned means, a slow release relay for maintaining said circuit operative for a prolonged period of time, and means momentarily actuated by successive ones of said notches to operate said relay, whereby said circuit is maintained operative after said last mentioned means has ceased to operate.

18. Film printing apparatus comprising the combination of a film operated breaker switch, a step by step rheostat controlled thereby, and means operative on movement of said breaker switch to one position for initiating control of the operation of said rheostat and for maintaining control of the operation of said rheostat when said breaker switch is moved to an alternate position.

19. The method of printing films which comprises directing at different times a plurality of light beams onto the same printing area, preparing a record of printing changes, moving said record with the films, cyclically rendering each beam ineffective to print and pre-setting its intensity while printing irom another pre-set beam, and controlling said rendering and presetting in timed relation with the movement of said record.

20. The method of printing onto a sensitized film from a printing film having sequences requiring difl'erent printer light intensities which comprises printing said sequences at the same printing point from a plurality of beams of light in cyclic order, preparing a record oi printing changes required by said sequences, moving said record with the films, and periodically adjusting the light intensity of the inactive beam in timed relation with the movement of said record while printing from another of said beams. V

21. Film apparatus comprising the combination of means providing a printing gate, a plurality of light beams therefor, film controlled means for rendering said beams active in cyclic order, and other film controlled means for adlusting the intensity of an inactive beam while printing from an adjusted beam.

22. Printing apparatus comprising the combination of a printing lamp, a step-by-step resistance device therefor having a certain number of steps, a rotary step-by-step switch having a number of contacts which is a sub-multiple of said steps, each of said contacts connected in multiple to steps on said resistance device which are separated by said number, and film 0perated means controlling said rotary switch to vary the resistance in circuit with said lamp.

23. Printing apparatus comprising the combination of a pair of printing lamps, light intensity controlling means for each of said lamps, a circuit for each of said means, a rotary stepby-step switch having contacts, alternate ones of said contacts being in one of said circuits and the remaining alternate contacts being in the other of said circuits, and film operated means controlling said rotary switch.

FREDERICK WILLIAM ROBERTS. 

